Vestel 17IPS20 power supply Q301 runs too hot

[alltvrepairs]

Hi,
Have just repaired this power supply after 4.7pF 2kv cap burnt.
Replaced the following:
U300 FAN6300
Q301 8N60C
R321 10R
R311 10R
C312 47pF 2KV

All Supplies are now fine and TV works great however noticed that the Mosfet is running too hot that barely can leave finger on heatsink for a couple of seconds. I have left TV ON for 18Hrs straight and still works but I know something is not right.
Usually a faulty snubber circuit causes this issue. Any known remedies for this common power supply?

[yokoono]

Re: Vestel 17IPS20 power supply Q301 runs too hot

D307, D512, D513, D351, D525, R329 they've been verified ?. An oscilloscope checks that the pulses in the mosfet gate are correct.

[lotas]

Re: Vestel 17IPS20 power supply Q301 runs too hot

Or maybe not a high-quality (fake) MOSFET with a high transition resistance Rds (on) and because of this it can get very hot.

[alltvrepairs]

Re: Vestel 17IPS20 power supply Q301 runs too hot

D307, D512, D513, D351, D525, R329 they've been verified ?. An oscilloscope checks that the pulses in the mosfet gate are correct.

Will double check again. Not checked with scope yet.

[alltvrepairs]

Re: Vestel 17IPS20 power supply Q301 runs too hot

Or maybe not a high-quality (fake) MOSFET with a high transition resistance Rds (on) and because of this it can get very hot.

The Mosfet was taken from a scrapped Panasonic PCB and was original. I have used 12N60 which should handle higher voltage.

But if I don't find any other faulty components I will replace again just in case.

[alltvrepairs]

Re: Vestel 17IPS20 power supply Q301 runs too hot

Update:
Found D307 (1N4148) open. Replaced but still Mosfet running too hot. Made no difference.

Replaced Mosfet to 4N60 from a donor board improved a lot the heat issue. It is still hotter than the temperature of the 2 other Mosfet Heatsinks on same Power supply but can leave finger on without hurting. Maybe I will actually use a thermometer to check again Mpsfet specs.
Left On overnight and still working

[yokoono]

Re: Vestel 17IPS20 power supply Q301 runs too hot

4n60= 4A/600V

[alltvrepairs]

Re: Vestel 17IPS20 power supply Q301 runs too hot

4n60= 4A/600V

Yes I know. Should be 6N60 but didn't have stock. But will change again with proper one. At least I have deduced that the MOSFET made a big difference.